The present invention relates to a process for the formation of a polymer film on an electrically conducting or semiconducting surface by electrografting employing an electrolytic solution including a Bronsted acid, and to the electrically conducting or semiconducting surfaces obtained by employing this process.
The preparation of electrically conducting or semi-conducting surfaces covered with polymer films is of great interest in numerous fields, in particular for the manufacture of electronic components or integrated optical devices, for the preparation of devices which can be used in the biomedical field or in biotechnologies (DNA chips, protein chips, and the like), for protection from corrosion, and for any modification to the surface properties of metals or semiconductors.
It appears to be accepted today that the preparation of grafted polymer films by electrografting of activated vinyl monomers to conducting surfaces proceeds by virtue of electro-initiation of the polymerization reaction starting from the surface, followed by growth of the chains, monomer by monomer. The reaction mechanism of electrografting has been described in particular in the papers by C. Bureau et al., Macromolecules, 1997, 30, 333; C. Bureau and J. Delhalle, Journal of Surface Analysis, 1999, 6(2), 159, and C. Bureau et al., Journal of Adhesion, 1996, 58, 101.
By way of example, the reaction mechanism of the electrografting of acrylonitrile by cathodic polarization can be represented according to SCHEME 1 below, in which the grafting reaction corresponds to stage No. 1, where the growth takes place starting from the surface; stage No. 2 being the main side reaction which results in the production of an ungrafted polymer:
